Will Power clinched victory in the second race of the Shell and Pennzoil Grand Prix of Houston doubleheader weekend, and while Power himself is no longer in the running for the 2013 IZOD IndyCar Series championship his success may still have important ramifications on who does get to walk away with this year's title.

Power's Penske team mate Helio Castroneves came into this weekend in the lead of the championship standings, but after a disastrous Saturday outing which saw him suffer costly gearbox issues his points lead over Scott Dixon had dwindled to almost nothing. That meant Sunday was time for some serious damage limitation work from the Brazilian.

To that end, Castroneves got an unexpected boost on Sunday - and it was thanks to the weather. Overnight storms had led to the washout of the morning's warm-up and qualifying sessions, leaving the grid lining up according to entrants points. That meant Castroneves had just lucked into pole position with Dixon joining him on the front row for the standing start, and there was every hope that with a moral booster like this Helio would be able to steady the ship and restore some of his championship lead.

The rain meant that the drivers had to be wary of damp patches lingering in parts of the 1.683-mile, 10-turn temporary street course, but on the plus side they were spared the hot, humid conditions that had roasted them for the first race on Saturday as they lined up for the start. As usual there was the initial aborted attempt to get the race underway, with Dario Franchitti stalling and Takuma Sato struggling and failing to get his car into the correct position further back.

Things were better the second time around, although an agonisingly long wait for the green light baited Marco Andretti into making a jump start which was swiftly penalised. Everyone got away cleanly with Castroneves maintaining his lead over championship rival Scott Dixon, while further back there were some early aggressive moves from Will Power and Ryan Hunter-Reay to make up positions while everyone was closely packed together.

The initial green flag stint only lasted three laps before the first full course caution, triggered by Simona de Silvestro hopping across the kerbs in turn 8; she just about made the corner but in doing so herded Graham Rahal into the tyre wall, also blocking the track for Tristan Vautier. De Silvestro was handed a drive-thru penalty for triggering the accident in the first place.

The race resumed single-file on lap 7 with Castroneves on point, but Dixon was yelling on the radio to tell his team that fluid was streaming out of the back of the race leader's car. It took a few minutes for the discharge from the #3 to become clear on the TV cameras but soon it was undeniable and race control were considering black flagging Castroneves when the situation emphatically resolved itself: Castroneves' gearbox housing failed catastrophically and the engine cut out at the start of lap 11. The Brazilian tried limping back to pit lane but the car didn't have it in it to make it round and finally died in turn 7 to trigger a new caution and signal disaster for his 2013 championship title hopes. The Penske crew got to work and rebuilt the car in record time, but Castroneves was down 36 laps by the time he was able to gingerly make his way back out onto the track.

That was a relief for Dixon whose car had by now been thoroughly soaked in oil, making traction all but impossible. It had allowed Castroneves' Penske team mate Will Power to get past the remaining traffic and take up residence on the tail end of the #9 for the restart, with Simon Pagenaud is third ahead of Justin Wilson, Ryan Hunter-Reay, James Hinchcliffe, Tony Kanaan and Charlie Kimball, while the biggest mover at this stage was Luca Filippi who was up to 12th place from 23rd on the grid in the #98 Bryan Herta Autosport car.

Racing resumed on lap 16 with Dixon relieved to at last be rid of the troublesome oil spill of a car in front and basking in the clear air ahead as he pulled clear of Power by a second and a half. Less happy was Pagenaud, whose handling fell away precipitously allowing Ryan Hunter-Reay to make an easy pass; the #77 was soon so slow that Justin Wilson had to check up to avoid running into the back of the Frenchman and in the process got jumped for position by James Hinchcliffe.

Pagenaud pitted for new tyres as soon as the fuel window was open on lap 27 to make it to the end of the race with only one more stop. Almost as soon as he came in, Luca Filippi's strong opening run ended up with nose-deep in a tyre wall after running wide on cold tyres on an out-lap after his own first stop; that brought out the fourth caution of the race and allowed the rest of the field to pit under yellow. Dixon won the race off pit road over Power, but by millimetres.

The restart lasted only a little over a lap before the next caution, but claimed two big names: Ryan Hunter-Reay's pace suddenly reduced to a crawl as he lost fourth gear and struggled to get back to pit lane for urgent repairs that cost him four laps; and more terminally, Tony Kanaan lost downforce while running behind Pagenaud and ended up running wide onto the marbles and into a crunching impact with the concrete wall at turn 7 on lap 34.

Having been bumped from behind twice in the build up to the restart on lap 40, Dixon seemed strangely discombobulated when the green flags came out and struggling for traction, allowing Power to make an easy pass to lead for the first time. A less than entirely impressed Dixon quickly recovered, and clamped himself onto the back of the #12 as the pair pulled away from the rest of the field partly thanks to the off-sync Sebastian Saavedra in third place holding up Hinchcliffe, Sebastien Bourdais and Justin Wilson until he came in at the end of lap 49.

Power and Dixon both came in for their next and final stops on lap 61, Power easily holding on to he lead after a glitch fitting the right rear wheel on the #9. The race was under caution almost the minute they exited pit lane, for Ed Carpenter who was stopped in the turn 3 run-off. The caution allowed the final pit stops of the day to play out with everyone now good to the finish, and Hinchcliffe having caught up to the leaders in third place ahead of Wilson, Bourdais and Pagenaud with race 1 pole sitter Takuma Sato in seventh ahead of Oriol Servia for the restart on lap 67, which lasted barely a few corners before bodywork from Josef Newgarden's car caused a quick debris caution in turn 9. Newgarden was also the cause of the next caution on lap 73 when he tipped Marco Andretti into a spin at turn 9 with the slightest of contacts which earned him a drive-thru for avoidable contact.

Power pulled away smartly at the green flag on lap 77 and held off Dixon's attempts to come back on him for the remaining 13 laps, which went green almost to the very end. Despite having more push-to-pass boosts left by the final lap, Dixon was never able to find a suitable opportunity to put them to good use before the race came to a premature end with a full course yellow coming just before the chequered flag. Power had succeeded not only in claiming victory, but in doing his team mate Castroneves a huge favour in terms of the points he's stolen away from Dixon in the process.

But all of those previously crucial developments were suddenly rendered secondary by the scenes unfolding in turn 5. Takuma Sato had got loose through the high speed bend and slid across the track right in front of Dario Franchitti: with no where to go, the #10 ran into and over the back of the AJ Foyt Racing car and was lifted up in the air where it spun into the catch fence and snapped round in sickening fashion.

Part of the catchfence itself was ripped out and thrown toward the grandstand along with a cloud of debris - leaving an estimated 15 fans requiring treatment of some sort - but the #10 was torn apart before it came to rest in the centre of the track. EJ Viso arrived next on the scene and successfully avoided Franchitti's wreck, but delivered a hefty secondary blow to the shattered #14 car just ahead.

"On the last lap I caught the marbles and brushed the wall and lost momentum," explained Sato. "A couple cars passed me as I was offline and in turn 5. I got very loose and Dario and I came together. Hopefully Dario is okay."

Viso was quickly out of his car, even having the foresight to pull away a piece of wreckage from the track to allow the rest of the cars to have a semblance of a path through the crash scene. Sato was also quickly up and about, but Franchitti wasn't in such good shape: while multiple witnesses reported him moving and waving his hands he was still unable to get out of the car before the medical extraction team arrived to free him and place him on a stretcher.

Team boss Chip Ganassi arrived at the scene shortly after, and confirmed to the media minutes later that Dario was awake and answering questions - understandably dazed, and complaining of a sore ankle and back, but much better than it could otherwise have been. He was transported directly to a nearby trauma centre where he was kept in overnight and diagnosed with two fractured vertebrae and a broken right ankle, along with a concussion. The back injury should not require surgery.

The IndyCar paddock breathed a sigh of relief, and smiles returned to the faces of Power, Dixon and Hinchcliffe as they carried out a still somewhat subdued podium presentation. Justin Wilson was satisfied with fourth ahead of Bourdais and Pagenaud, while Oriol Servia finished in seventh ahead of Charlie Kimball. Pagenaud's finish means that he is now mathematically ruled out of the championship battle, which had boiled down to a two-man duel between Dixon and Castroneves heading into to the final race of the season at Auto Club Speedway in Fontana, California in two weeks time.

All in all, Houston certainly hadn't been the smoothest of weekends for anyone involved, whether the race organisers battling track issues and weather or the Penske team battling chronic gearbox issues on Castroneves car. But that incident in turn 5 on the final lap had rather put all those niggles and frustrations firmly into their proper context.

Full race 2 results available.